Samuel K. Barber

Lawrence Berkeley National Laboratory

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J. van Tilborg

Lawrence Berkeley National Laboratory

Valeriy V. Yashchuk

Lawrence Berkeley National Laboratory

Wayne R. McKinney

Lawrence Berkeley National Laboratory

C. B. Schroeder

University of California, Berkeley

Fumika Isono

Lawrence Berkeley National Laboratory

C. G. R. Geddes

Lawrence Berkeley National Laboratory

Erik H. Anderson

Lawrence Berkeley National Laboratory

Eric Esarey

Lawrence Berkeley National Laboratory

Rossana Cambié

Lawrence Berkeley National Laboratory

Hai-En Tsai

Lawrence Berkeley National Laboratory

Cooperative Institutions

Lawrence Berkeley National Laboratory

University of California, Berkeley

University of California, Los Angeles

Czech Academy of Sciences, Institute of Physics

SLAC National Accelerator Laboratory

National Institutes for Quantum and Radiological Science and Technology

Keldysh Institute of Applied Mathematics

Lawrence Livermore National Laboratory

University of Michigan–Ann Arbor

University of California System

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Evolution of the laser's wavefront and mode during propagation through the amplifier and transport line of a 100-TW-class laser system

APS Division of Plasma Physics Meeting Abstracts (2020)

Curtis J. Berger J. van Tilborg Fumika Isono Samuel K. Barber Hai-En Tsai

Line (geometry)

Mode (computer interface)

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Optimal alignment of mirror based pentaprisms for scanning deflectometric devices

Lawrence Berkeley National Laboratory (2011)

Samuel K. Barber

In the recent work [Proc. of SPIE 7801, 7801-2/1-12 (2010), Opt. Eng. 50(5) (2011), in press], we have reported on improvement of the Developmental Long Trace Profiler (DLTP), a slope measuring profiler available at the Advanced Light Source Optical Metrology Laboratory, achieved by replacing the bulk pentaprism with a mirror based pentaprism (MBPP). An original experimental procedure for optimal mutual alignment of the MBPP mirrors has been suggested and verified with numerical ray tracing simulations. It has been experimentally shown that the optimally aligned MBPP allows the elimination of systematic errors introduced by inhomogeneity of the optical material and fabrication imperfections of the bulk pentaprism. In the present article, we provide the analytical derivation and verification of easily executed optimal alignment algorithms for two different designs of mirror based pentaprisms. We also provide an analytical description for the mechanism for reduction of the systematic errors introduced by a typical high quality bulk pentaprism. It is also shown that residual misalignments of an MBPP introduce entirely negligible systematic errors in surface slope measurements with scanning deflectometric devices.

Tracing

TRACE (psycholinguistics)

Systematic error

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Developmental long trace profiler using optimally aligned mirror based pentaprism

Lawrence Berkeley National Laboratory (2011)

Samuel K. Barber Gregory Y. Morrison Valeriy V. Yashchuk Mikhail V. Gubarev Ralf D. Geckeler

A low-budget surface slope measuring instrument, the Developmental Long Trace Profiler (DLTP), was recently brought into operation at the Advanced Light Source Optical Metrology Laboratory. The instrument is based on a precisely calibrated autocollimator and a movable pentaprism. The capability of the DLTP to achieve sub-microradian surface slope metrology has been verified via cross-comparison measurements with other high-performance slope measuring instruments when measuring the same high-quality test optics. In the present work, a further improvement of the DLTP is achieved by replacing the existing bulk pentaprism with a specially designed mirror based pentaprism. A mirror based pentaprism offers the possibility to eliminate systematic errors introduced by inhomogeneity of the optical material and fabrication imperfections of a bulk pentaprism. We provide the details of the mirror based pentaprism design and describe an original experimental procedure for precision mutual alignment of the mirrors. The algorithm of the alignment procedure and its efficiency are verified with rigorous ray tracing simulations. Results of measurements of a spherically curved test mirror and a flat test mirror using the original bulk pentaprism are compared with measurements using the new mirror based pentaprism, demonstrating the improved performance.

Curved mirror

TRACE (psycholinguistics)

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Stability of modulation transfer function calibration of surface profilometers using binary pseudo-random gratings and arrays with nonideal groove shapes

Optical Engineering (2010)

Samuel K. Barber Erik H. Anderson Rossana Cambié Stefano Marchesini Wayne R. McKinney

The major problem of measurement of a power spectral density (PSD) distribution of surface heights with surface profilometers arises due to the unknown modulation transfer function (MTF) of the instruments, which tends to distort the PSD at higher spatial frequencies. The special mathematical properties of binary pseudo-random patterns make them an ideal basis for developing MTF calibration test surfaces. Two-dimensional binary pseudo-random arrays have been fabricated and used for the MTF calibration of the MicroMap^TM-570 interferometric microscope with all available objectives. An investigation into the effects of fabrication imperfections on the quality of the MTF calibration and a procedure for accounting for such imperfections are presented.

Groove (engineering)

Optical transfer function

Modulation (music)

10.1117/1.3431659

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Citations (13)

Laser-Plasma - Accelerator-Driven Quasi - Monoenergetic MeV Thomson Photon Source and Laser Facility

Hai-En Tsai C. G. R. Geddes T. Ostermavr Gabriel Otero Munoz J. van Tilborg

In this report, we demonstrate precise control of a laser plasma accelerator (LPA) through characterization of a shock-induced density downramp injector. Experiments systematically varied the shock injector profile, including shock angle, shock position, up-ramp width, and acceleration length. As a result, an electron beam that was highly tunable from 30 to 300 MeV with 8.5% energy spread, 1.5 mrad divergence and 0.35 mrad pointing fluctuation was produced. We also report the progress of a project focusing on demonstrating the crucial enablers of a compact LPA based MeV Thomson photon source in an integrated experiment and a dedicated 100 TW laser facility built at the Berkeley Lab Laser Accelerator (BELLA) Center, Lawrence Berkeley National Laboratory (LBNL).

Advanced Photon Source

Plasma acceleration

10.1109/aac.2018.8659433

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Citations (1)

Binary pseudo-random gratings and arrays for calibration of the modulation transfer function of surface profilometers: recent developments

eScholarship (California Digital Library) (2009)

Samuel K. Barber Paul Soldate Erik H. Anderson Rossana Cambié Stefano Marchesini

Optical transfer function

Modulation (music)

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On the Asymmetric Focusing of Low-Emittance Electron Bunches via Active Lensing by Using Capillary Discharges

Bulletin of the American Physical Society (2017)

S. S. Bulanov G. A. Bagdasarov N. A. Bobrova A. S. Boldarev O. G. Olkhovskaya

Bunches

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Optimizing Down-Ramp Injection to Generate Stable and Tunable Electron Bunches for an LPA Driven FEL

Finn Kohrell Samuel K. Barber Kyle Jensen Curtis J. Berger C. B. Schroeder

Bunches

10.1109/aac55212.2022.10822920

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Optimization of the electron beam properties from intense laser pulses interacting with structured gas jets

Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIE (2017)

K. K. Swanson Hai-En Tsai Samuel K. Barber Rémi Lehe Hann-Shin Mao

Laser plasma acceleration has been intensely investigated for its ability to produce energetic, ultrashort electron bunches in a compact distance. A high intensity laser pulse propagating through a plasma expels the electrons from the optical axis via the ponderomotive force, leaving behind a column of ions and driving a density wake. The accelerating electric fields present in the wake can reach several orders of magnitude greater than those found in radio-frequency cavities, allowing for compact systems much smaller than those using conventional accelerators. This compact source can provide electrons for various applications including stages for a high energy collider or for production of x-ray pulses from coherent undulator radiation. However, these applications require tunable, stable and high-quality electron beams. We report on a study of controlled injection along a shock-induced density downramp of laser-plasma- accelerated electrons through precision tailoring of the density profile produced from a mm-scale gas jet. Using BELLA Center's TREX Ti:Sapphire laser, the effects of the plasma density profile and the tilt of the shock front on the beam spatial profile, steering, and energy were investigated experimentally. To explain these rela- tionships, we propose simple models which agree well with experimental results. Using this technique, electron beam quality was tailored, allowing for the production of high-quality electron beams with percent-level energy spreads over a range of energies.

10.1117/12.2266276

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Citations (1)

Binary pseudo-random gratings and arrays for calibration of the modulation transfer function of surface profilometers: recent developments

Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIE (2009)

Samuel K. Barber Paul Soldate Erik H. Anderson Rossana Cambié Stefano Marchesini

The major problem of measurement of a power spectral density (PSD) distribution of the surface heights with surface profilometers arises due to the unknown Modulation Transfer Function (MTF) of the instruments. The MTF tends to distort the PSD at higher spatial frequencies. It has been suggested [Proc. SPIE 7077-7, (2007), Opt. Eng. 47 (7), 073602-1-5 (2008)] that the instrumental MTF of a surface profiler can be precisely measured using standard test surfaces based on binary pseudo-random (BPR) patterns. In the cited work, a one dimensional (1D) realization of the suggested method based on use of BPR gratings has been demonstrated. Here, we present recent achievements made in fabricating and using two-dimensional (2D) BPR arrays that allow for a direct 2D calibration of the instrumental MTF. The 2D BPRAs were used as standard test surfaces for 2D MTF calibration of the Micromap^TM-570 interferometric microscope with all available objectives. The effects of fabrication imperfections on the efficiency of calibration are also discussed.

Optical transfer function

Spatial frequency

Modulation (music)

10.1117/12.825389

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Citations (9)